How to Build a Safe Deck

Assuring a family’s safety begins with knowing how to build a safe deck properly

By Ryaan J. Tuttle

Relaxing on the deck offers iconic backyard bliss, but too many homeowners rush into the project without considering the very real threat of deck collapse. Without proper support, decks run the risk of shearing away from the house eventually, endangering families and taking a big chunk of their homes down, too.

The key to build a safe deck that’s destined to last lies in paying close attention to building the proper connections into the home, securing the footings correctly and assuring the deck is properly flashed. Even some contractors get these steps wrong, so deck building is an advanced project requiring real skill and expertise.

Prepping the work area

The first step to build a safe deck is to measure out the deck and the home. Verify each of these measurements against blueprints to make sure your plans are sound. Next, remove some of the wood or vinyl siding to access the home’s sheathing.

Since the addition of the deck offers more opportunities for moisture to work its way beneath the surface, it’s important to install ice and water shielding over the sheathe, just like the shielding found on most rooftops.

Adding support

Bolt the first ledger or rim joist directly into the frame of the house. Check your state building codes before you begin. They’ll provide guidance on the proper bolts to use as well as the appropriate spacing and bolt pattern for your installation. This is a critical step, providing your deck with its first level of solid support.

Flashing

Next, install a piece of flashing over the ledger. The flashing works with your ice and water shielding to prevent moisture from working its way behind the ledger.

Moisture can cause rot, weakening the deck’s supports and damaging the home, so to build a safe deck take your time and assure the flashing is completely secure and flush with the surface of the home before nailing it into place.

Finding your footing

Deck footing provides the next layer of support. Lay out footings, checking them twice by measuring the distances against the blueprint. Once you’ve doublechecked the placement, you can dig.

You’ll dig as deep as your architect tells you to, but some of the depth will be determined by building codes. In Massachusetts, for example, local codes require holes that are 48 inches deep.

Once you’ve done your digging, call in a professional inspector to check the work up to this point. There’s no turning back once you start pouring the concrete, so if you want to build a safe deck it pays to be sure.

After the inspector gives you the go-ahead, insert Sonotube. Fill the Sonotube solid with concrete, all the way to the top.

Let the concrete cure, then install a metal post base anchor. Bolt the anchor directly into the concrete, where it will support the post base.

Building the deck

Now it’s time to frame up the deck. Build the frame 16 inches from center. Double all rim joists and bolt them directly into each post.

You’ll need to attach two tension ties directly to both the home and the deck. This is the third layer of support, another method of ensuring the deck will stay firmly in its place. This step is not optional as most building codes now require the use of these tension ties.

At this point the shape of the deck will come together. It’s all framed up now, and the frame is securely attached to the house and the posts.
The posts are secure in their concrete bases. With every bit of the frame solid and supported, add stairs, put on the decking, and add the trim boards.

Adding stairs

Stairs require the support of a concrete pad. You’ll need to dig a bed deep enough for a 10-inch solid pad, running the length of the deck. Let the concrete set and build the stairs on top of the pad. The stairs should be bolted directly into the frame of the deck so they remain sturdy and stable.

Decking and trim

The deck is now ready for composite decking and trim boards. A railing may also be needed. The deck shown here didn’t require one; it was less than 31 inches tall, which is the height where decks start requiring railings according to local building codes in Boston. Check your own local codes before deciding whether to include a rail.

Meanwhile, start finishing the deck by cutting the composite decking down to size. Leave a 1-inch overhang on each side. Secure the composite with composite decking screws. Screw them directly into the deck frame.

The composite’s job is to hide the frame and make the entire deck look finished. We recommend using the Cortex system to install it, as this system eliminates the need to nail boards down. Nails can rust or pop, making them far less ideal for the purposes of building a deck, which will remain sturdy and beautiful for years to come. The Cortex system also spares the deck owner from ever having to paint the deck.

Remain slow, steady and deliberate as you take each deck-building step. As eager as you may be to break out the lawn chairs, a deck job is nothing to rush.

Ryaan J. Tuttle is President of RJT Carpentry & Tile Inc. He has 15 years of experience in home remodeling and restorations and can be reached at rjtcarpentryandtile@gmail.com or 617-593-8632. For more information, visit the company’s Instagram page, @rjtcarpentryandtile.